Looking for clarity so I can move on...

I was in a relationship with my ex for 3 years. We lived in different places but it was manageable. She had been married to a guy 2 years before we got together. Her story was that he died from an overdose. I later found out that he died alone in their room while she was on a girl's trip. I really should have taken this as a red flag and I accept responsibility for that.

About year two she started making comments about dating someone closer to her. This after 2 years of trying my best to make it work.

I also found out later that she was living at home with her parents at 32 years of age.

Eventually she works up the balls to tell me that I've been good two her but she wants out. We chose to keep it civil . 2 weeks later she calls to check on me. During the conversation she tells me she met someone and is moving in with them. I later find out that this was an old boyfriend she was with before her marriage. Is it entirely possible that this was going on the whole time?